In a study of mate preference differences between men and women that spanned 37 cultures, buss (1989) found that men value youthful appearance more than women. Why

I believe the answer is: Youthful looks provide fertility clues.

According to evolutionary biologist, humans had the inherent isnticnt to mate and produce offsprings that have good chracteristics to survive in the environment. Fertility clues indicate that a woman is capable in producing such offspring (since women can no longer produce one after hitting a cetain age)